Estrogenic Activity of Perfluoro Carboxylic and Sulfonic Acids in Rainbow Trout Estrogen Receptor Binding and Liver Slice Vtg mRNA Expression Assays

Introduction: Perfluoroalkylated substances (PFAS) such as carboxylic acids, and sulfonic acids were manufactured in high quantities and are ubiquitous environmental contaminants. These chemicals persist in the environment and tend to bioaccumulate. Materials and Methods: In the current study, the estrogenic potential of a series of perfluoro carboxylic acids and select perfluoro sulfonic acids were assessed in an in vitro rainbow trout estrogen receptor (rtER) binding assay and an ex vivo rtER dependent vitellogenin ( Vtg ) expression rainbow trout liver slice assay. Results and Discussion: Perfluoro carboxylic acids with perfluoroalkyl chain lengths of four to six did not significantly bind to the rtER or induce Vtg expression in liver slices. Perfluoro carboxylic acids with chain lengths of seven to ten, and sulfonic acids with seven and eight carbon chains bound to the rtER, but with low relative binding affinities. While affinity for the rtER increased with increasing chain length the highest affinity measured was only 0.0025% relative to the endogenous hormone 17β-estradiol at 100%. Both the eight-carbon carboxylic acid and eight-carbon sulfonic acid induced Vtg expression in ex vivo liver slices. However, toxicity did not allow expression to achieve maximum efficacy relative to estradiol. Conclusion: Seven carbon and longer perfluoro carboxylic acids and sulfonic acids are capable of binding to the rtER and inducing ER dependent gene expression in rainbow trout liver slices, but toxicity seems have a greater effect than any adverse endocrine effect.